In the prior art, the techniques for providing a gas-tight seal between a tubular container and a plastic or elastomeric septum have generally involved either pressing the flat blunt end of the tube against the septum, or compressing the septum and inserting it inside the end of the tube so that the resulting expansion of the septum against the walls of the tube produces a sealing effect.
It has been found, however, that such techniques are not adequate for high-pressure chromatographic applications. Inadequate sealing may still occur when the septum is simply pressed against the blunt end. When using thin-bore tubular containers, where the septum is to be inserted inside the end of the tube, the tube must necessarily be large enough to accommodate the compressed septum. This imposes a lower practical limit on the size of the bore that can be conveniently used. Thus, heretofore, whether the septum was inserted inside the tube, or was pressed over the end of the tube, it was found that the temperature cycling utilized in chromatographic applications often caused shrinkage, and hence leakage, of the septum.